title: Unexpected cononsolvency behavior of poly (N-isopropylacrylamide)-based microgels.
abstract: Poly (N-isopropylacrylamide) (pNIPAm)-based microgels undergo a transition from fully water swollen (solvated) to deswollen (desolvated) as the temperature of the water they are dissolved in is increased >32 °C. In this submission, we examine how the temperature of this transition, i.e., the volume phase transition temperature (VPTT), depends on the concentration of methanol (MeOH) in water the microgels are dissolved in. To accomplish this, pNIPAm-based etalons are utilized, and it is shown that the VPTT for the microgels is much less than that previously observed for linear pNIPAm and pNIPAm-based microgels. Furthermore, and most interestingly, it is determined that the microgels can collapse in solutions containing high MeOH (>∼65% MeOH) concentration. This is in contrast to previous studies, which show that no VPTT is observed for pNIPAm in aqueous solutions containing >∼65% MeOH.
authors.affiliation: Department of Chemistry, University of Alberta, Edmonton, AB, T6G 2G2, Canada.
authors.forename: Ian N
authors.initials: IN
authors.lastname: Heppner
authors.forename: Molla R
authors.initials: MR
authors.lastname: Islam
authors.forename: Michael J
authors.initials: MJ
authors.lastname: Serpe
mesh_terms: D000180:Acrylic Resins / Q000138:chemical synthesis / Q000737:chemistry*; D005782:Gels / Q000138:chemical synthesis / Q000737:chemistry; D000432:Methanol / Q000737:chemistry; D013696:Temperature; D014867:Water / Q000737:chemistry
chemical_list: D000180:Acrylic Resins; D005782:Gels; D014867:Water; C052970:poly-N-isopropylacrylamide; D000432:Methanol
keywords: cononsolvency; microgel-based etalons; pNIPAm-based microgels; phase transitions; stimuli-responsive polymers